Air conditioner and method of controlling an air conditioner

ABSTRACT

An air conditioner and a method of controlling an air conditioner are provided. The air conditioner may include a main body that defines an outer appearance of the air conditioner, at least one indoor heat exchanger disposed within the main body, a plurality of branch tubes that guides a refrigerant into the at least one indoor heat exchanger, a circulation tube connected to the plurality of branch tubes to guide the refrigerant, a bypass tube that connects one of the plurality of branch tubes to the circulation tube, and a branch tube valve disposed in the one of the plurality of branch tubes to adjust a flow of the refrigerant flowing into the one of the plurality of branch tubes. The one of the plurality of branch tubes may have a diameter less than a diameter of each of the remaining branch tubes. In a cooling mode, the refrigerant may be introduced from the circulation tube into the at least one indoor heat exchanger through the one of the plurality of branch tubes. In a heating mode, the refrigerant may be discharged from the at least one indoor heat exchanger into the circulation tube through the bypass tube.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims priority under 35 U.S.C. 119 and 35 U.S.C. 365 to Korean Patent Application No. 10-2012-0130644, filed in Korea on Nov. 19, 2012, which is hereby incorporated by reference in its entirety.

BACKGROUND

1. Field

An air conditioner and a method of controlling an air conditioner are disclosed herein.

2. Background

Air conditioners and methods of controlling air conditioners are known. However, they suffer from various disadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein:

FIG. 1 is a graph illustrating air speed distribution according to position in an indoor heat exchanger;

FIG. 2 is a schematic perspective view of an indoor device of an air conditioner according to an embodiment;

FIG. 3 is a schematic diagram of an air conditioner according to an embodiment utilizing the indoor device of FIG. 2; and

FIG. 4 is a flowchart illustrating a method of controlling an indoor device of an air conditioner according to an embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to the embodiments, examples of which are illustrated in the accompanying drawings. Where possible, like reference numerals have been used to indicate like elements and repetitive description has been omitted.

In the following detailed description of embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments. These embodiments are described in sufficient detail to enable those skilled in the art to practice embodiments, and it is understood that other embodiments may be utilized and that logical structural, mechanical, electrical, and chemical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense.

Air conditioners are cooling/heating systems that cool an indoor space by repeatedly performing a series of operations, including suctioning indoor air, performing heat-exchange between a low-temperature refrigerant and the suctioned indoor air, and discharging the heat-exchanged air into the indoor space, or heat the indoor space by repeatedly performing the above operations for cooling in reverse. Such an air conditioner has a series of cycles involving a compressor, a condenser, an expansion valve, and an evaporator.

Air conditioners may be generally classified into separation type air conditioners, in which indoor and outdoor devices are separately installed, and integrated air conditioners in which indoor and outdoor devices are integrated. In recent years, separation type air conditioners have had an advantage in consideration of an installation space and noise.

An indoor device of such an air conditioner may include an indoor heat exchanger in which a refrigerant circulated into the air conditioner may be heat-exchanged with indoor air. The indoor air may absorb or dissipate heat through the heat-exchange with the refrigerant.

FIG. 1 is a graph illustrating air speed distribution according to position in an indoor heat exchanger. Referring to FIG. 1, a speed of air passing through the indoor heat exchanger may vary according to a vertical position in the indoor heat exchanger. However, as a refrigerant tube of the indoor heat exchanger has a same diameter regardless of a vertical position in the indoor heat exchanger, it may be difficult to efficiently perform heat-exchange.

FIG. 2 is a schematic perspective view of an indoor device of an air conditioner according to an embodiment. Although a ceiling type indoor device is shown in FIG. 2, embodiments are not limited to a ceiling type indoor device.

Referring to FIG. 2, an indoor device 100 of an air conditioner according to an embodiment may include a front panel 120 that defines an edge portion of an outer appearance of a bottom surface thereof, a suction grill 130 disposed in or at a central portion of the front panel 120 to introduce indoor air into the indoor device 100, a cabinet 140 that defines an upper outer appearance of the indoor device 100 and including a plurality of components therein, and a base 150 that covers a top surface of the cabinet 140 and configured to mount the indoor device 100 on or in a ceiling. An overall outer appearance of the indoor device 100 may be defined by the front panel 120, the suction grill 130, the cabinet 140, and the base 150.

The front panel 120 may be punched in a square shape so that the suction grill 130 may be mounted therein. Also, one or more discharge holes 160, which may have a rectangular shape, may be defined in a bottom surface of the front panel 120. The one or more discharge holes 160 may discharge air heat-exchanged within the indoor device 100 again into an indoor space. For example, front, rear, left, and right portions of the front panel 120 may be punched in a same shape to define the one or more discharge holes, respectively.

Also, a louver 170 configured to force a flow direction of the air discharged into the indoor space through each of the one or more discharge holes 160 may be disposed in the respective discharge hole 160. The louver 170 may have a square plate shape corresponding to a shape and size of the respective discharge hole 160. The louver 170 may be connected to a motor (not shown) to generate a rotation force to rotate the louver 170, thereby forcing or controlling a flow direction of air.

The suction grill 130 having an approximately square shape may be mounted in or at a central portion of the front panel 120. As described above, the suction grill 130 may suction indoor air into the indoor device 100. Thus, a plurality of suction holes 180, which may be longitudinally cut in a horizontal direction and vertically penetrate the suction grill 130, may be defined in or at a central portion of the suction grill 130.

A blower device (not shown) that forcibly introduces the indoor air into the indoor device 100 and a heat exchanger 200 in which the air introduced into the indoor device 100 may be heat-exchanged with the refrigerant may be disposed above the suction grill 130, for example, within the cabinet 140.

The indoor heat exchanger 200 may include a tube which may be bent several times. The tube may have a predetermined distance between the bent portions thereof. Also, the indoor air may pass through or along a predetermined distance.

The indoor heat exchanger 200 may be vertically disposed between the front panel 120 and the base 150. That is, the indoor heat exchanger 200 may be vertically disposed with respect to the ground. Also, the indoor heat exchanger 200 may include a plurality of heat exchangers, which may be vertically separated from each other. That is, each of the plurality of heat exchangers constituting the indoor heat exchanger 200 may be horizontally disposed with respect to the ground, and the plurality of heat exchangers may be vertically stacked on each other. Also, the plurality of heat exchangers may be vertically arranged to be spaced apart from each other. A detailed structure of the indoor heat exchanger 200 will be described hereinbelow.

FIG. 3 is a schematic diagram of an air conditioner according to an embodiment utilizing the indoor device of FIG. 2. Referring to FIG. 3, an air conditioner 10 according to an embodiment may include a main body 50 that defines an outer appearance of the air conditioner 10, a circulation tube 11, in which a refrigerant which is a working fluid may be circulated, a compressor 12 that compresses a suctioned refrigerant and discharge the compressed refrigerant, an outdoor heat exchanger 14 in which the refrigerant is heat-exchanged with outdoor air, an expansion device 15 that expands the refrigerant passing therethrough, and the indoor device 100. Also, the compressor 12, the outdoor heat exchanger 14, the expansion device 15, and the indoor device 100 may be connected to the circulation tube 11.

The indoor device 100 may include the indoor heat exchanger 200, branch tubes 210 and 220 that connect the circulation tube 11 to the indoor heat exchanger 200, and an indoor expansion valve 230 that expands the refrigerant introduced into the indoor heat exchanger 200.

The indoor heat exchanger 200 may include a plurality of heat exchangers 200 a, 200 b, and 200 c, which may be distinguished according to upper and lower positions thereof. The plurality of heat exchangers may be independently provided, or may each constitute a portion of a refrigerant tube.

The plurality of heat exchangers 200 a, 200 b, and 200 c may be referred to as first heat exchanger 200 a, second heat exchanger 200 b, and third heat exchanger 200 c when defined from a heat exchanger located adjacent to the front panel 120. That is, the plurality of heat exchangers 200 a, 200 b, and 200 c may be referred to as third heat exchanger 200 c, second heat exchanger 200 b, and first heat exchanger 200 a when defined from a heat exchanger located adjacent to base 150. In this embodiment, for convenience of description, the indoor heat exchanger including three heat exchangers will be described as an example. However, embodiments are not limited in the number of heat exchangers.

The branch tubes 210 and 220 may include a plurality of cooling mode inflow-side branch tubes and a plurality of cooling mode discharge-side branch tubes, which may be respectively connected to sides of the indoor heat exchanger 200. The cooling mode inflow-side branch tube(s) 210 and the cooling mode discharge-side branch tube(s) 220 may be vertically spaced apart from each other.

According to an operation mode of the air conditioner 10, the cooling mode inflow-side branch tube 210 may be referred to as a heat mode discharge-side branch tube 210. Similarly, the cooling mode discharge-side branch tube 220 may be referred to as a heat mode inflow-side branch tube 220. Hereinafter, the air conditioner according to embodiments on the basis of a flow direction of a refrigerant in a cooling mode will be described hereinbelow.

The cooling mode inflow-side branch tube 210 may include first, second, and third cooling mode inflow-side branch tubes 210 a, 210 b, and 210 c, which may be disposed between the outdoor heat exchanger 14 and the indoor heat exchanger 200 to respectively guide a refrigerant into the first, second, and third heat exchangers 200 a, 200 b, and 200 c. Similarly, the cooling mode discharge-side branch tube 220 may include first, second, and third cooling mode discharge-side branch tubes 220 a, 220 b, and 220 c, which may be disposed between the indoor heat exchanger 200 and the compressor 12 to respectively guide a refrigerant into the first, second, and third heat exchangers 200 a, 200 b, and 200 c.

Referring to FIG. 1, a speed of air passing through the first heat exchanger 200 a disposed at a lower side may be relatively slower than a speed of air passing though the second or third heat exchanger 200 b or 200 c. Thus, the first inflow-side branch tube 210 a disposed at a lower side may have a diameter less than a diameter of the other branch tubes. That is, the first inflow-side branch tube 210 a having a relatively small diameter may be connected to the first heat exchanger 200 a in which a flow rate of air passing through may be relatively less among the plurality of heat exchangers. That is, the branch tube 210 may have a diameter to correspond to a flow rate of air passing through the heat exchanger 200 connected to the branch tube 210. Thus, when the cooling operation is performed, an amount of refrigerant introduced into the first heat exchanger 200 a disposed at the lower side may be less than an amount of refrigerant introduced into the other heat exchangers 200 b and 200 c.

A branch tube valve 250 to adjust an amount of refrigerant flowing into the first cooling mode inflow-side branch tube 210 a may be disposed in the first cooling mode inflow-side branch tube 210 a. The branch tube valve 250 may be a solenoid valve, which is selectively openable, or an electric expansion valve (EEV), for which an opened degree is adjustable. Also, the branch tube valve 250 may be a check valve to guide a refrigerant in only one direction. In this case, the check valve may guide a refrigerant so that the refrigerant is introduced into the first heat exchanger 200 a through the first cooling mode inflow-side branch tube 210 a in the cooling mode and prevent a refrigerant from being discharged from the first heat exchanger 200 a through the first cooling mode inflow-side branch tube 210 a in the heating mode.

As the first cooling mode inflow-side branch tube 210 a (the first heating mode discharge-side branch tube) has a diameter less than a diameter of the first cooling mode discharge-side branch tube 220 a (the first heating mode inflow-side branch tube), when the indoor device is converted in operation mode to perform the heating mode, the refrigerant introduced into the first cooling mode discharge-side branch tube 220 a may be stagnated in the first cooling mode inflow-side branch tube 210 a. To prevent the above-described phenomenon from occurring, a bypass tube 260 may be connected between the first cooling mode inflow-side branch tube 210 a and the circulation tube 11.

The bypass tube 260 may be configured so that a portion of the refrigerant discharged from the indoor heat exchanger 200 bypasses the branch tube 210 and then is introduced into the circulation tube 11. The bypass tube 260 may have a first end connected to the first cooling mode inflow-side branch tube 210 a and a second end connected between the expansion device 15 and the cooling mode inflow-side branch tube 210. That is, the bypass tube 260 may have a first end connected to the first heating mode discharge-side branch tube 210 a and the second end connected between the expansion device 15 and the heating mode discharge-side branch tube 210 a.

The bypass tube 260 may have a diameter greater than a diameter of the first cooling mode inflow-side branch tube 210 a. Also, the bypass tube 260 may have the same diameter as a diameter of the second cooling mode inflow-side branch tube 210 b or the third cooling mode inflow-side branch tube 210 c. Also, the bypass tube 260 may have a diameter that corresponds to a diameter of the first cooling mode discharge-side branch tube 220 a. In the heating mode, a refrigerant may be guided from the first heat exchanger 200 a to the expansion device 15 through the bypass tube 260 having a sufficient diameter without the stagnation phenomenon.

A bypass valve 265 to adjust an amount of refrigerant flowing into the bypass tube 260 may be disposed in or on the bypass tube 260. The bypass valve 265 may be opened in the heating mode and closed in the cooling mode. Thus, it may prevent a refrigerant from being introduced into the first heat exchanger 200 a through the bypass tube 260 in the cooling mode. The bypass valve 265 may be, for example, a solenoid valve or an EEV valve. Also, the bypass valve 265 may be a check valve to guide a refrigerant in only one direction. In this case, the check valve may prevent a refrigerant from being introduced into the first heat exchanger 200 a through the bypass tube 260 in the cooling mode and guide a refrigerant so that the refrigerant is discharged from the first heat exchanger 200 a through the bypass tube 260 in the heating mode.

According to embodiments, the first cooling mode inflow-side branch tube 210 a disposed at the lower side may be changed in structure to improve cooling efficiency. In the heating mode, as a refrigerant introduced into the indoor heat exchanger 200 mainly has a gaseous state, the refrigerant is not significantly influenced by gravity. However, in the cooling mode, a refrigerant introduced into the indoor heat exchanger 200 may be mainly in a liquid state. Thus, unlike a speed or amount distribution of air, the refrigerant may be significantly influenced by gravity. As a result, a larger amount of refrigerant may be introduced into the branch tube 210 a disposed at the lower side. Therefore, in embodiments disclosed herein, the lower-side inflow branch tube may be designed to have a small diameter in the cooling mode. Thus, an optimum passage may be designed in the cooling mode on the basis of the air speed distribution in the upper and lower positions of the heat exchanger in the cooling mode.

It is noted that the first heating mode inflow-side branch tube 220 a may be changed in structure to design an optimum passage in the heating mode as well. However, detailed description with respect to the design of the optimum passage has been omitted.

FIG. 4 is a flowchart illustrating a method of controlling an indoor device of an air conditioner according to an embodiment. The method of controlling the indoor device of the air conditioner will be described with reference to FIG. 4. The method may be implemented in an air conditioner, such as that shown in FIG. 3.

When an air conditioner, such as air conditioner 10 shown in FIG. 3, is turned on, in step S100, an operation mode of the air conditioner may be determined, in step S110. When the determined operation mode is a cooling mode, a bypass valve, such as bypass valve 265 shown in FIG. 3, may be closed or turned off, in step S120. As the bypass valve is closed/turned off, it may prevent a refrigerant from being introduced into a bypass tube, such as bypass tube 260 shown in FIG. 3.

Then, the branch tube valve may be opened/turned on, in step S130. As the branch tube valve is opened or turned on, refrigerant may be introduced into a first heat exchanger, such as first heat exchanger 200 a of FIG. 3, through first cooling mode inflow-side branch tube, such as first cooling mode inflow-side branch tube 210 a of FIG. 3.

When the determined operation mode is a heating mode, the bypass valve may be opened/turned on, in step S140. As the bypass valve is opened/turned on, refrigerant discharged from the first heat exchanger may smoothly flow through the bypass tube without a stagnation phenomenon.

Then, the branch tube valve may be closed/turned on, in step S150. As the branch tube valve is closed/turned off, refrigerant is prevented from being discharged from the first heat exchanger into the first heating mode discharge-side branch tube.

As described above, when the bypass valve or the branch tube valve is a check valve, an operation for controlling the bypass valve or the branch tube valve may be omitted.

According to embodiments disclosed herein, an amount of guided refrigerant may vary according to vertical positions of the indoor heat exchanger to improve heat-exchange efficiency and performance of the air conditioner. Also, an optimum refrigerant passage in the cooling mode may be designed to improve cooling efficiency. Also, when a heating operation is performed, refrigerant may be bypassed through the predetermined bypass tube to prevent a refrigerant stagnation phenomenon from occurring, which may occur according to the optimized design for cooling from occurring.

Embodiments disclosed herein provide an air conditioner and a control method thereof.

Embodiments disclosed herein provide an air conditioner that may include a main body that defines an outer appearance; an indoor heat exchanger disposed within the main body; a plurality of branch tubes that guides a refrigerant introduced into the indoor heat exchanger; a circulation tube connected to the plurality of branch tubes to guide the refrigerant; a bypass tube that connects a portion of the plurality of branch tubes to the circulation tube; and a branch tube valve disposed in a portion of the plurality of branch tubes to adjust a flow of the refrigerant flowing into the portion of the plurality of branch tubes. The portion of the plurality of branch tubes may have a diameter less than that of each of the remaining branch tubes. In a cooling mode, the refrigerant may be introduced from the circulation tube into the indoor heat exchanger through the portion of the plurality of branch tubes, and in a heating mode, the refrigerant may be discharged from the indoor heat exchanger into the circulation tube through the bypass tube.

The branch tube valve may enable the refrigerant to flow in the cooling mode and block a flow of the refrigerant in the heating mode. The indoor heat exchanger may include a plurality of heat exchangers vertically spaced apart from each other, and the plurality of branch tubes may be connected to the plurality of heat exchangers, respectively.

The portion of the plurality of branch tubes may be connected to a heat exchanger having a small amount of air flowing therethrough among the plurality of heat exchangers. The bypass tube may have a diameter greater than the portion of the plurality of branch tubes. A lower-side branch tube of the plurality of branch tubes may have a diameter less than that of an upper-side branch tube.

A bypass valve that adjusts a flow of the refrigerant flowing into the bypass tube may be disposed in the bypass tube. The bypass valve may block a flow of the refrigerant in the cooling mode and enable the refrigerant to flow in the heating mode.

Each of the valves may include one of a solenoid valve, an electric expansion valve, or a check valve. The branch tube valve may include a check valve that prevents the refrigerant from being discharged from the indoor heat exchanger through the portion of the plurality of branch tubes in the heating mode. The bypass valve may include a check valve that prevents the refrigerant from being introduced into the indoor heat exchanger through the bypass tube in the cooling mode.

Embodiments disclosed herein further provide an air conditioner that may include a main body that defines an outer appearance; a circulation tube in which a refrigerant flows; a first heat exchanger disposed in or at a side of the main body; a first inflow-side branch tube that guides the refrigerant from the circulation tube into the first heat exchanger in a cooling mode; a second heat exchanger disposed above the first heat exchanger; a second inflow-side branch tube that guides the refrigerant from the circulation tube into the second heat exchanger in the cooling mode; and a bypass tube that bypasses the refrigerant, which may be introduced from the first heat exchanger into the first branch tube, into the circulation tube in a heating mode. The first inflow-side branch tube may have a diameter less than that of the second inflow-side branch tube.

A branch tube valve that selectively opens or closes the first inflow-side branch tube may be disposed in the first inflow-side branch tube, and a bypass valve that selectively opens or closes the bypass tube may be disposed in the bypass tube.

The bypass tube may have a diameter greater than that of the first inflow-side branch tube. The bypass tube may have the same diameter as that of the second inflow-side branch tube.

Embodiments disclosed herein further provide a method for controlling an air conditioner including a plurality of indoor heat exchangers, a plurality of branch tubes respectively connected to the plurality of indoor heat exchangers, and a refrigerant circulation tube connected to the plurality of branch tubes. The method may include selectively closing a first branch tube having a small diameter of the plurality of branch tubes on the basis of an operation mode of the air conditioner; and allowing a refrigerant discharged from the indoor heat exchangers to bypass the first branch tube, thereby selectively closing a bypass tube guiding the refrigerant into the circulation tube on the basis of the operation mode of the air conditioner. When one of the bypass valve and a branch tube valve may be opened, the other one may be closed.

When the air conditioner is in a cooling mode, the bypass valve may be turned off, and the branch tube valve may be turned on. When the air conditioner is in a heating mode, the bypass valve may be turned on, and the branch tube valve may be turned off.

Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art. 

What is claimed is:
 1. An air conditioner, comprising: a main body that defines an outer appearance of the air conditioner; at least one indoor heat exchanger disposed within the main body; a plurality of branch tubes that guides a refrigerant introduced into the at least one indoor heat exchanger; a circulation tube connected to the plurality of branch tubes to guide the refrigerant; a bypass tube that connects one of the plurality of branch tubes to the circulation tube; and a branch tube valve disposed in the one of the plurality of branch tubes to adjust a flow of the refrigerant flowing in the one of the plurality of branch tubes, wherein the one of the plurality of branch tubes has a diameter less than a diameter of each of the remaining branch tubes.
 2. The air conditioner according to claim 1, wherein in a cooling mode, the refrigerant is introduced from the circulation tube into the at least one indoor heat exchanger through the one of the plurality of branch tubes, and in a heating mode, the refrigerant is discharged from the at least one indoor heat exchanger into the circulation tube through the bypass tube.
 3. The air conditioner according to claim 2, wherein the branch tube valve enables flow of the refrigerant in the cooling mode and blocks flow of the refrigerant in the heating mode.
 4. The air conditioner according to claim 2, wherein the at least one indoor heat exchanger comprises a plurality of heat exchangers vertically spaced apart from each other, and wherein the plurality of branch tubes are connected to the plurality of heat exchangers, respectively.
 5. The air conditioner according to claim 4, wherein the one of the plurality of branch tubes is connected to a heat exchanger having a smaller amount of air flowing therethrough among the plurality of heat exchangers.
 6. The air conditioner according to claim 2, wherein the bypass tube has a diameter greater than a diameter of the one of the plurality of branch tubes.
 7. The air conditioner according to claim 2, wherein a branch tube of the plurality of branch tubes at a lowermost position has a diameter less than a diameter of a tube at an uppermost position.
 8. The air conditioner according to claim 2, wherein a bypass valve that adjusts a flow of the refrigerant flowing into the bypass tube is disposed in the bypass tube.
 9. The air conditioner according to claim 8, wherein the bypass valve blocks a flow of the refrigerant in the cooling mode and enables the refrigerant to flow in the heating mode.
 10. The air conditioner according to claim 8, wherein the bypass valve comprises a check valve that prevents the refrigerant from being introduced into the at least one indoor heat exchanger through the bypass tube in the cooling mode.
 11. The air conditioner according to claim 2, wherein the branch tube valve comprises one of a solenoid valve, an electric expansion valve, or a check valve.
 12. The air conditioner according to claim 2, wherein the branch tube valve comprises a check valve that prevents the refrigerant from being discharged from the at least one indoor heat exchanger through the one of the plurality of branch tubes in the heating mode.
 13. An air conditioner, comprising: a main body that defines an outer appearance of the air conditioner; a circulation tube in which a refrigerant flows; a first heat exchanger disposed in the main body; a first branch tube that guides the refrigerant from the circulation tube into the first heat exchanger in a cooling mode; a second heat exchanger disposed above the first heat exchanger; a second branch tube that guides the refrigerant from the circulation tube into the second heat exchanger in the cooling mode; and a bypass tube that bypasses the refrigerant, which is introduced from the first heat exchanger into the first branch tube, into the circulation tube in a heating mode, wherein the first branch tube has a diameter less than a diameter of the second branch tube.
 14. The air conditioner according to claim 13, wherein a branch tube valve that selectively opens or closes the first branch tube is disposed in the first branch tube, and a bypass valve that selectively opens or closes the bypass tube is disposed in the bypass tube.
 15. The air conditioner according to claim 13, wherein the bypass tube has a diameter greater than a diameter of the first branch tube.
 16. The air conditioner according to claim 13, wherein the bypass tube has the same diameter as a diameter of the second branch tube.
 17. A method for controlling an air conditioner comprising a plurality of indoor heat exchangers, a plurality of branch tubes, respectively, connected to the plurality of indoor heat exchangers, and a refrigerant circulation tube connected to the plurality of branch tubes, the method comprising: selectively closing a first branch tube of the plurality of branch tubes having a small diameter than the remaining branch tubes of the plurality of branch tubes on a basis of an operation mode of the air conditioner; and allowing a refrigerant discharged from the plurality of indoor heat exchangers to bypass the first branch tube, thereby selectively closing a bypass tube that guides the refrigerant into the circulation tube on the basis of the operation mode of the air conditioner.
 18. The method according to claim 17, wherein the air conditioner further includes a branch tube valve disposed in the first branch tube and a bypass valve disposed in the bypass tube, and wherein, when one of the bypass valve or the branch tube valve is opened, the other one is closed.
 19. The method according to claim 18, wherein, when the air conditioner is in a cooling mode, the bypass valve is turned off or closed, and the branch tube valve is turned on or opened.
 20. The method according to claim 18, wherein, when the air conditioner is in a heating mode, the bypass valve is turned on or opened, and the branch tube valve is turned off. 